1. Field of the Invention
This invention relates generally to wrenches and more particularly to wrenches of the type wherein a fluid input reciprocably drives a lever arm which unidirectionally turns an output shaft adapted to be operatively engaged with a driven object such as a work tool, e.g. a removable socket.
2. Description of the Prior Art
Manual ratchet-type wrenches are adapted to apply a torque through a lever arm, directly to a socket placed over a bolt or nut to be threadably tightened. Electric motors and hydraulic or pneumatic reciprocating or rotating power sources have been utilized to greatly increase the torque applied directly to the socket. These power sources apply torque to tighten the nut or bolt about the longitudinal axis of the threaded connection to be made.
Ratchet-type wrenches connectable to a pressurized hydraulic fluid source are also known in the art wherein the pressurized fluid is utilized to reciprocate a piston within a cylinder to drive a lever arm. Such wrenches utilize the reciprocating piston and cylinder combination to in turn reciprocably move a pawl which tangentially impacts a ratchet drive wheel, turning the nut or bolt to be tightened. The ratchet-type wrenches of this type which are currently available do not maximize the torque available from the force of the reciprocating piston since a relatively small mechanical advantage is available between the input force and the torque applied to the nut or bolt, the lever arm being relatively short. The lever arm of the prior art extends laterally away from the longitudinal axis of the wrench. The piston-cylinder combination is located along a side of the wrench, connecting to the lever arm. Because the lever arm is perpendicular to the length of the wrench, keeping the prior art hydraulic wrenches relatively wide, the lever arm is ideally kept relatively short in order to keep the size of the wrench within limits.
A further shortcoming of prior art hydaulic wrenches is the fact that the oscillating input force arises from the piston reciprocating within the cylinder. The piston must work the pawl at one end of the piston-cylinder combination. This arrangement requires a pivoting connection at the other end of the piston-cylinder combination, because the overall length of the piston-cylinder combination changes as the piston extends to impact the pawl. Pivotably connecting one end of the combination allows for automatic adjustment to this change in overall length.
The prior art hydraulic wrenches use a conventional piston reciprocating within a cylinder. Not only must the piston-cylinder combination be pivoted, as discussed above, but the combination must also be guarded for safety. The prior art does guard the piston-cylinder, but does not completely enclose them to provide a fail safe system.
It is often useful to use wrench extensions to reach out of the way threaded connections. An example of such a connection would be the main bearing nuts on some diesel engines, which are accessible only through small doors in the side of the crank case.
Wrenches using the hydraulic principle previously known in the art and discussed briefly above, are of some advantage in that flexible hydraulic lines can be used as an extension means, but because of the lateral position of the hydraulic cylinder the wrench itself is wide at the output end and therefore not acceptable in some situations.
Socket wrenches adaptable as wrench extensions are shown in reissue Pat. No. 23,661, issued May 26, 1953 to E. T. Able et al. and U.S. Pat. No. 3,564,953 which issued Feb. 23, 1971 to E. T. Able. Both of the preceding patents utilize a rotary power source releasably connected to the input end of the extension to turn the output end of the extension.
Hydraulic pressure is particularly suitable to certain situations encountered in industry. It is often necessary as a result of specifications for a given piece of machinery to apply a set amount of torque to a threaded connection. Torque applied to a given nut or bolt is directly related to hydraulic pressure. Hydraulic pressure can be calibrated to specific values of torque with relative ease, as compared with other motive inputs.